Two stage process for the production of unsaturated carboxylic acids by oxidation of lower unsaturated hydrocarbons

A process for production of carboxylic acid using a two-stage catalytic vapor-phase oxidation of olefins comprises

• introducing into a first stage reactor, a feedstream comprising olefins, oxygen, steam and inert gas;
• contacting the feedstream in the first stage reactor with a catalyst composition comprising a catalyst having the formula
• MoaPdbBicFedX1eX2fX3gOz
• wherein
• X1=at least one or more of Co, Ni, V, Pt, Rh
• X2=at least one or more of Al, Ga, Ge, Mn, Nb, Zn, Ag, P, Si, W
• X3=at least one or more of K, Mg, Rb,Ca, Sr, Ba, Na
• O=oxygen
• a is 1,
• 0<b≦0.3,
• 0<c≦0.9,
• 0<d≦0.9,
• 0<e≦0.9,
• 0<f≦0.9,
• 0<g≦0.3,
• z is a number which satisfies the valences of the other elements in the formula,
• said contacting in the first stage reactor being under reaction conditions sufficient to produce a first stage product comprising aldehyde;
• introducing the first stage product into a second stage reactor;
• contacting the first stage product in the second stage reactor with a catalyst composition comprising a catalyst having the formula
• Moa1Vb1Alc1Xd1Ye1Oz1
• wherein
• X=W or Mn or both
• Y=at least one or more of Pd, Sb, Ca, P, Ga, Ge, Si, Mg, Nb, K
• O is the valence oxygen, and
• a is 1,
• b is 0.01 to 0.9,
• 0<c≦0.2,
• 0<d≦0.5,
• 0<e≦0.5,
• z is a number which satisfies the valences of the other elements in the formula;
• and
• said contacting in the second stage reactor being under conditions sufficient to produce a second stage product comprising carboxylic acid.